Golf ball

ABSTRACT

A layer of a golf ball is formed of a golf ball-forming composition in which a silicone rubber powder, silicone resin powder or composite powder thereof is blended in an elastomer, resin or butadiene rubber base. The composition is easy to remove from a mold after molding, and the golf ball has advantages including high durability against consecutive strikes, and good feel and rebound even at low temperature.

[0001] This invention relates to a golf ball having a portion or layerformed of a golf ball-forming composition which is easy to remove from amold after molding.

BACKGROUND OF THE INVENTION

[0002] In prior art two-piece golf balls, the core is typically formedfrom rubber materials based on highly resilient polybutadiene rubber andheat crosslinked with a peroxide and a co-crosslinking agent such asmethacrylic acid. The cover is commonly formed of ionomer resinsfeaturing impact resistance and cut resistance, commercially availableunder the trade name of Surlyn and Himilan.

[0003] The two-piece golf balls are generally given the advantages ofdistance and durability at the sacrifice of a soft feel, which is veryimportant to golf players. Efforts were made to develop two-piece golfballs with a soft feel by making the core softer and the cover harder.These golf balls, however, suffer from other problems. Some golf ballsare less durable against consecutive strikes, some lack reboundcharacteristics, and some have poor low-temperature performance.

[0004] As a result of the ensuing development work, there were marketedgolf balls whose core or cover has a two layer structure in whichresilience is assigned to one layer and a feel is assigned to the otherlayer.

[0005] The ionomer resins favored as the cover material and thecrosslinked polybutadiene favored as the core material manifest goodresilience at a high hardness, but tend to lose resilience as thehardness lowers. While polyurethane elastomers, polyamide elastomers andpolyester elastomers are advantageously used as the cover intermediatelayer for imparting a comfortable feel, they are desired to have furtherresilience and the reduced dependency of hardness on temperature.

[0006] An attempt was then made to blend millable type silicone rubberin polybutadiene, followed by peroxide crosslinking (JP-A 60-258236).Problems arise with respect to the dispersion of silicone rubber inpolybutadiene. Non-uniform reactivity leads to low durability againststrikes. This combination is then very difficult to consistently providegood physical properties.

[0007] Another attempt was made to blend millable type silicone rubberin a core-forming rubber or cover-forming resin, followed by dynamiccrosslinking (JP-A 8-243191 and JP-A 9-220296). These blends havedrawbacks including extremely reduced flow, difficulty of injectionmolding, and difficulty of uniform dispersion, which lead to lowdurability against strikes. It is very difficult to tailor these blendsto a practically acceptable level.

[0008] The development of a new material is indispensable to impartdesirable characteristics to the golf ball. In the golf ball industry,there is a need for a material having further increased resilience toenable better flight performance, softness, and stable physicalproperties over a wide temperature range.

SUMMARY OF THE INVENTION

[0009] An object of the invention is to provide a golf ball formed of amaterial which is easy to mold and maintains stable softness and highresilience over a wide temperature range.

[0010] According to the invention, there is provided a golf ballcomprising a portion formed of a golf ball-forming composition havingblended therein at least one of a silicone rubber powder, a siliconeresin powder, and a composite powder thereof.

[0011] Preferably, the composite powder comprises silicone rubberparticles surface coated with a silicone resin; the silicone rubberpowder comprises crosslinked dimethylpolysiloxane and/ormethylphenylpolysiloxane microparticulates; the silicone resin powdercomprises cured polyorganosilsesquioxane microparticulates. Typicallythe silicone rubber powder, silicone resin powder, and composite powderare of spherical particles and have a particle size of 0.5 to 50 μm anda particle size distribution ranging from 0.1 to 100 μm. The siliconerubber powder, silicone resin powder, and composite powder havefunctional groups borne thereon. The silicone rubber powder, siliconeresin powder, and composite powder thereof are preferably blended in anamount of 0.5 to 50% by weight of the composition.

[0012] The golf ball-forming composition is typically at least onemember selected from among a one-piece golf ball material, a corematerial and a cover material for a two-piece golf ball, a corematerial, an intermediate layer material and a cover material for amulti-piece golf ball having at least three pieces.

[0013] In one preferred embodiment, the golf ball-forming composition isbased on at least one member selected from among an ethylene ionomerresin, polyester elastomer, polyurethane elastomer, polyolefinelastomer, polyamide elastomer, polyolefin resin, and styrene blockcopolymer. The preferred ethylene ionomer resin is anethylene-(meth)acrylic acid copolymer neutralized with a monovalentand/or divalent metal ion or an ethylene-(meth)acrylicacid-(meth)acrylate terpolymer neutralized with a metal ion. Theethylene ionomer resin preferably has a Shore D hardness of 40 to 80 anda (meth)acrylic acid content of 5 to 25% by weight.

[0014] In another preferred embodiment, the golf ball-formingcomposition is based on a rubber material comprising a polybutadienecontaining at least 40% of cis-1,4 bonds and an unsaturated carboxylicacid or metal ion or both for crosslinking the polybutadiene.

[0015] We have found that by blending an appropriate amount of a finepowder of polysiloxane structure such as a silicone rubber powder,silicone resin powder or composite powder thereof in a golf ball-formingcomposition, more specifically by blending a silicone powder in thecured state from the first rather than crosslinking a millable typesilicone rubber with a golf ball-forming material as in the prior art,the composition is significantly improved in mold release necessary toenable in-mold shaping and injection molding. In addition, a golf ballformed therefrom is improved in flight performance and durabilityagainst consecutive strikes and offers a very soft feel when hit.

[0016] When a silicone rubber powder, silicone resin powder or compositepowder thereof is blended in a golf ball-forming composition (e.g., amaterial to form the center, core, cover, cover layer or one-piece golfball), preferably in an amount of 0.5 to 50% by weight based on thecomposition, a golf ball formed therefrom is given excellentmoldability, resilience and low-temperature properties which have neverbeen achieved with conventional golf ball materials. That is, the golfball has improved flight performance and durability against consecutivestrikes as well as a very soft feel when hit. The invention ispredicated on these findings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a schematic view of a three-piece golf ball according toone embodiment of the invention.

[0018]FIG. 2 is a schematic view of a two-piece golf ball according toanother embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] The golf ball of the invention requires that at least one powderin the cured state selected from among a silicone rubber powder, asilicone resin powder, and a composite powder thereof be blended in agolf ball-forming composition.

[0020] The silicone rubber powder used herein is, for example, amicroparticulate product of high polymeric stereostructure obtained bycrosslinking a linear dimethylpolysiloxane and/ormethylphenylpolysiloxane having at least 0.05 mol % of vinyl groupsadded thereto with methylhydrogenpolysiloxane as a crosslinking agent,or a modified one thereof. The silicone rubber powder preferably has atrue specific gravity of approximately 0.97. Suitable powder inspherical particle form is commercially available, for example, underthe trade name of KMP597, 598, 594 and 595 and in irregular particleform under the trade name of X-52-875, all from Shin-Etsu Chemical Co.,Ltd.

[0021] The silicone resin powder used herein is, for example, amicroparticulate cured polyorganosilsesquioxane in which siloxane bondsare cured to form a three-dimensional network represented by(RSiO_(3/2))_(n), or a modified one thereof. It is recommended that R inthe formula be CH₃, C₆H₅ or long-chain alkyl. The silicone resin powderpreferably has a true specific gravity of approximately 1.3. Suitablepowder in spherical particle form is commercially available, forexample, under the trade name of KMP590, X-52-1186 and X-52-854 fromShin-Etsu Chemical Co., Ltd. Suitable powder of the type modified withvinyl, epoxy and amino groups are available under the trade name ofX-52-821, X-52-830 and X-52-831, from Shin-Etsu Chemical Co., Ltd.

[0022] The composite silicone powder used herein comprises siliconerubber particles which are surface coated with a silicone resin, boththe silicone rubber and the silicone resin being as described above. Thecomposite silicone powder preferably has a true specific gravity of 1.0to 0.98. Suitable powder is commercially available, for example, underthe trade name of KMP600 and X-52-1139G from Shin-Etsu Chemical Co.,Ltd.

[0023] Whether it is silicone rubber, silicone resin or compositesilicone type, the silicone powder used herein may be either a powder ofspherical particles or a powder of irregular particles, with thespherical particle powder being preferred.

[0024] It is very easy to add the silicone powder to rubbers or resinswhich are conventionally used as the base of golf ball-forming materialsbecause the silicone particles are effectively dispersible therein. Forfurther improved compatibility with rubbers or resins, a silicone powderbearing functional groups such as vinyl, epoxy and amino groups isadvantageously used.

[0025] The silicone powder preferably has a mean particle size of atleast 0.5 μm, more preferably at least 0.6 μm, further preferably atleast 2 μm, and up to 50 μm, more preferably up to 30 μm, furtherpreferably up to 15 μm, most preferably up to 6 μm. A powder with toosmall a mean particle size may scatter in the dispersion step and beawkward to the manufacture whereas a powder with too large a meanparticle size may be poorly dispersible and ineffective for improvingdurability against strikes.

[0026] Also preferably, the silicone powder has a particle sizedistribution ranging from 0.1 μm, more preferably from 1 μm, to 100 μm,more preferably to 30 μm, further preferably to 15 μm, most preferablyto 10 μm. A narrower particle size distribution ensures more uniformdispersion.

[0027] The golf ball of the invention should include at least oneconstituent layer having the silicone powder blended therein.Specifically, at least one constituent layer is formed of a golfball-forming composition having an appropriate amount of the siliconepowder blended therein.

[0028] Independent of the type of the silicone powder and the type ofbase polymer of the composition, an appropriate amount of the siliconepowder blended is at least 0.5%, especially at least 5% by weight and upto 50%, especially up to 30% by weight based on the weight of the basepolymer (or golf ball-forming composition). Beyond the upper limit,uniform dispersion may become difficult, resulting in losses ofresilience and durability against consecutive strikes. Below the lowerlimit, the addition effect of the silicone powder may becomeunascertainable.

[0029] While at least one constituent layer of a golf ball is formed ofa golf ball-forming composition having the silicone powder blendedtherein, the golf ball-forming composition may be any of well-knowncompositions used in golf balls, for example, compositions based onrubbers or thermoplastic resins for the center of wound golf balls,rubbers or thermoplastic resins for the core or core layer of solid golfballs, rubbers or thermoplastic resins for the outermost layer (cover)or inner layer of wound golf balls or solid golf balls.

[0030] Illustrative examples of the base polymer in the golfball-forming composition include polybutadiene containing at least 40%of cis-1,4 bonds, styrene block copolymers, polyurethane elastomers,polyester elastomers, polyamide elastomers, polyolefin elastomers,polyolefin resins, and ethylene ionomer resins.

[0031] The polybutadiene exemplified as the base of a rubber compositionis one containing at least 40% of cis-1,4 bonds, preferably at least 70%of cis-1,4 bonds. Suitable polybutadiene may be selected from well-knownones, for example, BROL from JSR. The polybutadiene is typically used asmaterials to form the solid center of wound golf balls and the core andinner layer (excluding outer layer or cover) of solid golf balls. Thepolybutadiene containing at least 40% of cis-1,4 bonds is advantageouslyused as the materials to form the solid center of wound golf balls andthe core of solid golf balls. Where polybutadiene containing at least40% of cis-1,4 bonds is blended in the golf ball-forming composition, acarboxylic acid and/or metal ion-containing compound is preferably usedfor crosslinking purposes. Suitable compounds are zinc oxide andmagnesium stearate.

[0032] The styrene block copolymers used herein includestyrene-butadiene-styrene block copolymers (SB and SBS),styrene-isoprene-styrene block copolymers (SI and SIS), and hydrogenatedproducts thereof (SEB, SEBS, SEP, SEPS). They are commercially availableunder the trade name of Califlex TR and Kraton G from Shell Chemical andSepton from Kurare K.K.

[0033] The polyurethane elastomers used herein include well-knownthermoplastic and thermosetting polyurethane elastomers. A commerciallyavailable example is Pandex from Dainippon Ink Chemical K.K.

[0034] The polyester elastomers used herein include well-knownthermoplastic polyester elastomers. A commercially available example isHytrel from Dupont-Toray K.K.

[0035] The polyamide elastomers used herein include well-knownthermoplastic polyamide elastomers. A commercially available example isPebax from Toray K.K.

[0036] The polyolefin elastomers used herein include well-known dynamiccrosslinking polyolefin elastomers. They are commercially availableunder the trade name of Santoprene from Monsanto Co. and Dynalon(hydrogenated polybutadiene) from JSR.

[0037] The polyolefin resins used herein include linear low-densitypolyethylene, ethylene-(meth)acrylic acid copolymers, andethylene-(meth)acrylic acid-(meth)acrylate copolymers.

[0038] The ethylene ionomer resins used herein include copolymers ofα-olefin and α,β-unsaturated carboxylic acid in which carboxyl groupsare neutralized with mono- or divalent metal ions; and copolymers ofα-olefin, α,β-unsaturated carboxylic acid and α,β-unsaturatedcarboxylate in which carboxyl groups are neutralized with mono- ordivalent metal ions.

[0039] Examples of the α-olefin include those of 2 to 8 carbon atoms,especially 2 to 6 carbon atoms. Exemplary α,β-unsaturated carboxylicacids are acrylic acid, methacrylic acid, maleic acid, and fumaric acid.The α,β-unsaturated carboxylates include esters of about 4 to 12 carbonatoms, for example, methyl (meth)acrylate, ethyl (meth)acrylate,isobutyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl(meth)acrylate, with isobutyl (meth)acrylate being most preferred.

[0040] An appropriate acid content is 5 to 25%, more preferably 7 to20%, most preferably 10 to 15% by weight based on the entire weight ofthe ionomer resin. An ionomer resin with too low an acid content may beless resilient whereas an ionomer resin with too high an acid contentmay be less flexible. The content of (meth)acrylate is preferably atleast 5%, more preferably at least 8% by weight, and up to 45%, morepreferably up to 30% by weight based on the entire weight of the ionomerresin. Too low a (meth)acrylate content may make it difficult to form afully flexible composition whereas too high a (meth)acrylate content maygive a composition which is too flexible to provide cutting resistance.

[0041] Exemplary metal ions used for neutralization in the ionomerresins are Na, Li, Zn, Mg, K and Ca. The degree of neutralization isusually at least 10 mol %, more preferably at least 30 mol % while itsupper limit is up to 90 mol %, especially up to 80 mol %. Too low adegree of neutralization may lead to the lack of resilience whereas toohigh a degree of neutralization may interfere with the flow duringmolding.

[0042] The ethylene ionomer resin preferably has a Shore D hardness of40 to 80, more preferably 45 to 75.

[0043] Suitable ionomer resins are commercially available under thetrade name of Himilan from Dupont-Mitsui Polychemical K.K., Surlyn fromE. I. Dupont and Iotek from Exxon Corp.

[0044] In the practice of the invention, the ethylene ionomer resin andolefin resin are advantageously used as a material to form the innerlayer and outer layer (cover) in three or more layer structure golfballs, and especially as the cover material.

[0045] The polyester elastomer, polyurethane elastomer, polyolefinelastomer, polyamide elastomer, polyolefin resin and styrene blockcopolymer should preferably have a Shore D hardness of at least 10, morepreferably at least 20, while its upper limit is preferably up to 50,especially up to 40. A resin material having a hardness within thisrange is advantageously used as a material to form the solid center ofwound golf balls, the core of solid golf balls, and the inner layer ofthree or more layer structure golf balls, and especially as the innerlayer material.

[0046] Depending on the particular portion of the golf ball which isformed of the composition, suitable additives can be blended in theabove-described base polymer. Exemplary additives are pigments,dispersants, antioxidants, and UV absorbers and added in customaryamounts. Additionally, inert fillers such as zinc oxide, barium sulfate,titanium dioxide, silica, calcium carbonate and zinc carbonate;polyethylene wax and metal soaps may also be added for the purposes ofspecific gravity adjustment in accordance with the standards of golfball as well as coloring.

[0047] According to the invention, the silicone powder is blended in thegolf ball-forming composition described above. An appropriatecompounding method is selected from well-known methods for compoundinggolf ball-forming materials. For example, when the silicone powder isblended in polybutadiene rubber, a mixer commonly used for rubber,typically a Banbury mixer or roll mill is employed. Where the siliconepowder is blended in the thermoplastic resin, a mixer commonly used forresins, typically a single or twin-screw extruder or roll mill isemployed.

[0048] The core, intermediate layer or outer layer can be formed by anyof methods commonly used in conventional golf ball molding. In a coremolding example using polybutadiene rubber, the rubber composition iscompression or injection molded in a core-forming mold where thecomposition is heat cured by heating at a sufficient temperature for thecrosslinking agent and co-crosslinking agent to act (e.g., at about 130to 170° C. for 5 to 40 minutes when the crosslinking agent andco-crosslinking agent are dicumyl peroxide and zinc acrylate,respectively). The core is formed in this way.

[0049] When the intermediate layer and outer layer (cover) are moldedfrom the thermoplastic resin, any of methods commonly used inconventional golf ball molding is acceptable. For example, the coreprepared by the above method is placed in a mold, in which thethermoplastic resin composition is compression or injection molded so asto enclose the core.

[0050] The shape of the respective layers thus formed is not critical.Often, the core preferably has a diameter of at least 25 mm, especiallyat least 27 mm and up to 42 mm, especially up to 40 mm. The solid centerpreferably has a diameter of at least 15 mm, especially at least 20 mmand up to 40 mm, especially up to 38 mm. With a core or center diameteroutside the range, resilience and/or durability against consecutivestrikes may become insufficient. The one-piece solid golf ballpreferably has a diameter of 40 mm to 43 mm so that it may have anapproximate outer diameter as the authorized golf ball.

[0051] In the event where the golf ball-forming composition is used inwound golf balls, the composition is advantageously used to form thesolid center, intermediate layer or cover (enclosing the thread rubberlayer). The wound golf ball includes a wound core in the form of a solidor liquid center on which thread rubber is wound. The wound core ismanufactured by any well-known method, usually by winding thread rubberaround the center. The thread rubber layer thus formed preferably has athickness of at least 1 mm, especially at least 1.5 mm and up to 4.4 mm,especially up to 4.0 mm. Outside the range, a loss of resilience or aloss of durability against consecutive strikes may become noticeable.

[0052] Where the intermediate layer or outer layer of multi-piece golfballs is formed from the golf ball-forming composition according to theinvention, that layer should preferably have a thickness of at least 0.5mm, especially at least 1 mm and up to 3 mm, especially up to 2.5 mm.Outside the range, a loss of resilience or a loss of durability againstconsecutive strikes may become noticeable. The intermediate layer orouter layer should preferably have a Shore D hardness of from 15 to 80,more preferably from 25 to 70. Specifically the intermediate layer (orinner layer) should preferably have a Shore D hardness of from 20 to 75,more preferably from 30 to 60; and the outer layer (cover) shouldpreferably have a Shore D hardness of from 40 to 80, more preferablyfrom 45 to 65. Outside the range, a loss of resilience, a loss ofdurability against consecutive strikes or degradation of feel may becomenoticeable.

[0053] The golf ball is formed with a plurality of dimples on itssurface. The geometrical arrangement of dimples may be octagonal oricosahedral arrangement while the dimple pattern may be any of square,hexagon, pentagon and triangle patterns.

[0054] The diameter and weight of the golf ball are set in accordancewith the Rules of Golf, specifically to a diameter of not less than42.67 mm and a weight of not greater than 45.93 grams.

EXAMPLE

[0055] Examples of the invention are given below by way of illustrationand not by way of limitation. All parts are by weight.

[0056] Referring to FIGS. 1 and 2, there are illustrated three andtwo-piece golf balls which were prepared in the Examples. Thethree-piece golf ball shown in FIG. 1 include a core (a) or (b), anintermediate layer 3, and an outer layer 1. The two-piece golf ballshown in FIG. 2 include a core (c) or (d) and an outer layer 1. All thelayers are disposed in a concentric fashion so that a radially outsidelayer encloses a radially inside layer.

[0057] Core-forming compositions were formulated in accordance withTable 1, milled in a Banbury mixer and conventionally molded at 155° C.for 15 minutes, forming cores. It is noted that the core (d) in Table 1was obtained by premixing 10 parts of silicone rubber TSE 2287U with 0.5part of peroxide TC-8 on a roll mill and compounding the premix with theremaining components.

[0058] The components in Tables 1 to 3 are shown below.

[0059] BROL: polybutadiene rubber by JSR

[0060] Hytrel 3046: polyester elastomer, Shore D hardness 30, byDupont-Toray K.K.

[0061] Hytrel 4047: polyester elastomer, Shore D hardness 40, byDupont-Toray K.K.

[0062] Himilan 1706: Zn-neutralized ionomer resin, acid content 15%,Shore D hardness 62, by Dupont-Mitsui Polychemical K.K.

[0063] Himilan 1605: Na-neutralized ionomer resin, acid content 15%,Shore D hardness 62, by Dupont-Mitsui Polychemical K.K.

[0064] Himilan AM7318: Na-neutralized ionomer resin, acid content 18%,Shore D hardness 65, by Dupont-Mitsui Polychemical K.K.

[0065] Himilan AM7317: Zn-neutralized ionomer resin, acid content 18%,Shore D hardness 65, by Dupont-Mitsui Polychemical K.K.

[0066] Himilan 1601: Na-neutralized ionomer resin, acid content 10%,Shore D hardness 60, by Dupont-Mitsui Polychemical K.K.

[0067] Himilan 1557: Zn-neutralized ionomer resin, acid content 12%,Shore D hardness 58, by Dupont-Mitsui Polychemical K.K.

[0068] TSE 2287U: millable type silicone rubber, JIS-A hardness 80, byToshiba Silicone K.K.

[0069] TC-8: 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane 50% paste, byToshiba Silicone K.K.

[0070] KMP597: silicone rubber powder, spherical, mean particle size 5μm, particle size distribution 1-10 μm, true specific gravity 0.97,water content 0.1%, by Shin-Etsu Chemical Co., Ltd.

[0071] X-52-830: silicone resin powder, spherical, mean particle size 2μm, particle size distribution 1-8 μm, true specific gravity 1.3, watercontent 1%, epoxy group introduced, by Shin-Etsu Chemical Co., Ltd.

[0072] KMP600: composite silicone powder, spherical, mean particle size5 μm, particle size distribution 1-15 μm, true specific gravity 1.00,water content 0.1%, by Shin-Etsu Chemical Co., Ltd.

[0073] XER-91: carboxyl group-modified, crosslinked rubber (NBR)particles, mean particle size 0.07 μm, by JSR IM-301: carboxylgroup-modified acrylic monomer “core/shell polymer,” mean particle size0.1-0.7 μm, by Takeda Pharmaceutical K.K. TABLE 1 (a) (b) (c) (d) CorePolybutadiene BR01 100 100 100 90 Formulation Zinc diacrylate 25 25 2626 (pbw) Dicumyl peroxide 1.2 1.2 1.2 1.2 Zinc oxide 5 5 5 5 Bariumsulfate 21.5 21.5 17.0 17.0 Antioxidant 0.2 0.2 0.2 0.2 Peptizer 0.1 0.10.1 0.1 KMP 597 10 TSE 2287U (TC-8) 10 Physical Diameter (mm) 35.2 35.238.7 38.7 properties Hardness (mm) 3.9 3.9 3.1 3.1 Weight (g) 27.1 27.535.6 35.9 Initial velocity 76.55 76.65 76.55 76.30 @ 23° C. (m/s)

[0074] Intermediate and outer layer-forming resin compositions wereblended in accordance with Tables 2 and 3 and compounded on a twin-screwextruder.

[0075] As noted above, the core (d) of Comparative Example 6 wasprepared by compounding polybutadiene with millable type siliconerubber, and molding the compound concomitant with crosslinking andcuring.

[0076] The intermediate layer of Comparative Example 7 was prepared frommillable type silicone rubber by compounding 100 parts of TSE 2287U with0.5 part of TC-8, sheeting the compound, wrapping the pre-formed corewith the sheets, effecting primary vulcanization at 170° C. for 10minutes in a core-molding press, taking out the core, and effectingsecondary vulcanization at 200° C. for 4 hours. The resulting core isthe silicone intermediate layer-bearing core.

[0077] On the cores, covers or outer layers were molded as shown inTables 2 and 3, obtaining golf balls.

[0078] The golf balls were tested as follows, with the results alsoshown in Tables 2 and 3. Many measurements were made both at roomtemperature (23° C.) and at a low temperature (3° C.).

[0079] Hardness is a deflection (mm) under an applied load of 100 kg.

[0080] Initial velocity was measured at 23° C. and 3° C. on apparatusapproved by USGA.

[0081] Flight distance (including carry and total) was determined at 23°C. and 3° C. by hitting the ball with a driver (#1W) at a head speed(HS) of 45 m/s using a hitting machine by True Temper Co.

[0082] Slope is the slope of a correlation line between initialvelocities at 23° C. and 3° C.

[0083] Durability against strikes was determined by repeatedly hittingthe ball with a driver (#1W) at a head speed of 40 m/s using a hittingmachine by True Temper Co., with the maximum being 300 strikes. In eachexample, five balls were tested. The number of broken balls and anaverage of the strikes at which the balls were broken are reported.

[0084] Feel was rated at 23° C. and 3° C. by five low-handicap amateurgolfers using a driver, No. 5 iron and putter.

[0085] VS: very soft and pleasant

[0086] S: soft and good

[0087] Av: ordinary

[0088] H: hard TABLE 2 Example 1 2 3 4 5 6 7 Material (pbw) Core a a a aa c b (Table 1) Intermediate Layer Hytrel 4047 100 100 100 100 100Hytrel 3046 100 X-52-830 5 Cover or outer layer Himilan 1706 50 50 50 5050 50 Himilan 1605 50 50 50 50 50 50 Himilan AM7318 50 Himilan AM7317 50KMP597 10 10 10 X-52-830 5 KMP600 10 Titanium dioxide 3 3 3 3 3 3 3Structure Core Diameter (mm) 35.2 35.2 35.2 35.2 35.2 38.7 35.2 Hardness(mm) 3.9 3.9 3.9 3.9 3.9 3.3 3.9 Weight (g) 27.1 27.1 27.1 27.1 27.135.6 27.5 Initial Velocity 76.55 76.55 76.55 76.55 76.55 76.55 76.65 @23° C. (m/s) Intermediate layer Outer diameter (mm) 38.7 38.7 38.7 38.738.7 — 38.7 Hardness (mm) 3.7 3.7 3.7 3.7 3.7 — 3.7 Weight (g) 35.6 35.635.6 35.6 35.6 — 35.8 Initial velocity 75.76 75.76 75.76 75.76 75.92 —75.95 @ 23° C. (m/s) Ball (after outer layer molding and painting)Diameter (mm) 42.7 42.7 42.7 42.7 42.7 42.7 42.7 Hardness (mm) 3.3 3.03.2 3.3 3.0 3.3 3.0 Weight (g) 45.2 45.2 45.2 45.2 45.2 45.2 45.5Initial Velocity 76.84 77.15 76.70 76.77 76.92 76.81 77.06 @ 23° C.(m/s) Initial Velocity 75.96 76.26 75.77 75.88 76.02 75.93 76.18 @ 3° C.(m/s) Slope 0.0440 0.0445 0.0465 0.0445 0.0450 0.0440 0.0440 Flightperformance Distance @ 23° C., HS 45 Carry (m) 218.6 220.0 218.0 218.5219.0 218.5 219.5 Total (m) 233.5 235.0 233.0 233.0 233.5 233.2 234.0Distance @ 3° C., HS 45 Carry (m) 213.5 214.5 212.0 213.0 213.5 213.4214.0 Total (m) 227.7 230.1 227.3 228.2 228.1 227.5 228.8 Durabilityagainst strikes Number of broken balls/ 0/5 0/5 0/5 0/5 0/5 0/5 0/5 testballs Average of strikes at not not not not not not not breakage (300strikes at broken broken broken broken broken broken broken maximum)Feel @ 23° C. Putter VS VS VS VS S VS S Iron VS VS VS VS VS VS VS DriverVS VS S VS VS VS VS Feel @ 3° C. Putter VS VS VS VS VS VS VS Iron VS VSVS VS VS VS VS Driver VS VS VS VS VS VS VS

[0089] TABLE 3 Example 1 2 3 4 5 6 7 Material (pbw) Core a a a a c d a(Table 1) Intermediate Layer Hytrel 4047 100 100 100 100 TSE 2287U 100Cover or outer layer Himilan 1706 50 50 50 50 50 50 Himilan 1605 50 5050 50 50 50 Himilan 1601 50 Himilan 1557 50 XER-91 10 IM-301 10 Titaniumdioxide 3 3 3 3 3 3 3 Structure Core Diameter (mm) 35.2 35.2 35.2 35.238.7 38.7 35.2 Hardness (mm) 3.9 3.9 3.9 3.9 3.3 3.3 3.9 Weight (g) 27.127.1 27.1 27.1 35.6 35.9 27.1 Initial Velocity 76.55 76.55 76.55 76.5576.55 76.30 76.35 @ 23° C. (m/s) Intermediate layer Outer diameter (mm)38.7 38.7 38.7 38.7 — — 38.7 Hardness (mm) 3.7 3.7 3.7 3.7 — — 3.7Weight (g) 35.6 35.6 35.6 35.6 — — 35.8 Initial velocity 75.73 75.7375.73 75.73 — — 75.33 @ 23° C. (m/s) Ball (after outer layer molding andpainting) Diameter (mm) 42.7 42.7 42.7 42.7 42.7 42.7 42.7 Hardness (mm)3.0 3.1 3.3 3.3 3.0 3.0 3.0 Weight (g) 45.2 45.2 45.2 45.2 45.2 45.545.3 Initial Velocity 76.58 76.22 76.65 76.58 76.71 76.50 76.32 @ 23° C.(m/s) Initial Velocity 75.43 75.16 75.52 75.48 75.55 75.55 75.41 @ 3° C.(m/s) Slope 0.0575 0.0530 0.0565 0.0550 0.0580 0.075 0.0475 Flightperformance Distance @ 23° C., HS 45 Carry (m) 217.0 214.4 217.5 216.5217.5 216.5 215.0 Total (m) 232.0 229.5 231.8 231.2 232.0 231.5 230.0Distance @ 3° C., HS 45 Carry (m) 209.0 207.0 210.0 209.5 210.5 208.5209.0 Total (m) 224.5 221.0 224.2 223.2 224.3 223.9 222.8 Durabilityagainst strikes Number of broken balls/ 5/5 3/5 2/5 2/5 5/5 5/5 5/5 testballs Average of strikes at 260 260 290 290 260 220 80 breakage (300strikes at maximum) Feel @ 23° C. Putter S VS VS VS H H VS Iron S S VSVS H H VS Driver S S VS VS AV AV VS Feel @ 3° C. Putter AV S S S H H VSIron AV AV S S H H VS Driver AV AV S S H AV VS

[0090] As seen from Tables 2 and 3, the three and two-piece golf ballsof Examples 1-4 and 6 in which an appropriate amount of silicone rubberpowder, silicone resin powder or composite silicone powder was added tothe outer layer ionomer resin were superior in rebound and flightperformance to the two-piece golf ball of Comparative Example 5 and eventhe three-piece golf balls of Comparative Examples 1 and 2 in which suchpowder was not added.

[0091] The balls within the scope of the invention were also improved inlow-temperature performance factors including rebound (as represented bythe slope of a temperature-initial velocity correlation line), flightdistance and feel, and durability against consecutive strikes. They werefar superior to the three-piece golf ball of Comparative Example 3 inwhich crosslinked diene rubber powder was added to the outer layer(cover) and the three-piece golf ball of Comparative Example 3 in whichthe carboxyl group-modified acrylic monomer polymer was added to theouter layer (cover), which were contemplated in the past. The golf ballsof Comparative Example 7 in which millable type silicone rubber was usedin the intermediate layer and Comparative Example 6 in which the corehad millable type silicone rubber and polybutadiene co-cured showedshort flight distances because of insufficient rebound and very poordurability against consecutive strikes.

[0092] Similar molding and ball performance advantages were found withthe ball of Example 5 in which silicone rubber powder was added to thethermoplastic polyester elastomer in the intermediate layer and the ballof Example 7 in which silicone rubber powder was added to the corerubber.

[0093] The golf balls of the invention have the advantage of easyremoval from a mold after molding, remain durable against consecutivestrikes, and provide a satisfactory feel and rebound even at lowtemperature.

[0094] Japanese Patent Application No. 11-361060 is incorporated hereinby reference.

[0095] Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A golf ball comprising a portion formed of a golf ball-formingcomposition having blended therein at least one of a silicone rubberpowder, a silicone resin powder, and a composite powder thereof.
 2. Thegolf ball of claim 1 wherein the composite powder comprises siliconerubber particles surface coated with a silicone resin.
 3. The golf ballof claim 1 wherein the silicone rubber powder comprises crosslinkeddimethylpolysiloxane or methylphenylpolysiloxane microparticulates orboth.
 4. The golf ball of claim 1 wherein the silicone resin powdercomprises cured polyorganosilsesquioxane microparticulates.
 5. The golfball of claim 1 wherein the silicone rubber powder, silicone resinpowder, and composite powder thereof have a particle size of 0.5 to 50μm and a particle size distribution ranging from 0.1 to 100 μm.
 6. Thegolf ball of claim 1 wherein the silicone rubber powder, silicone resinpowder, and composite powder thereof are blended in an amount of 0.5 to50% by weight of the composition.
 7. The golf ball of claim 1 whereinthe silicone rubber powder, silicone resin powder, and composite powderthereof comprise spherical particles.
 8. The golf ball of claim 1wherein the silicone rubber powder, silicone resin powder, and compositepowder thereof have functional groups.
 9. The golf ball of claim 1wherein the golf ball-forming composition is at least one memberselected from the group consisting of a one-piece golf ball material, acore material and a cover material for a two-piece golf ball, a corematerial, an intermediate layer material and a cover material for amulti-piece golf ball having at least three pieces.
 10. The golf ball ofclaim 1 wherein the golf ball-forming composition is based on at leastone member selected from the group consisting of an ethylene ionomerresin, polyester elastomer, polyurethane elastomer, polyolefinelastomer, polyamide elastomer, polyolefin resin, and styrene blockcopolymer.
 11. The golf ball of claim 10 wherein the ethylene ionomerresin is an ethylene-(meth)acrylic acid copolymer neutralized with amonovalent or divalent metal ion or both or an ethylene-(meth)acrylicacid-(meth)acrylate terpolymer neutralized with a metal ion.
 12. Thegolf ball of claim 10 wherein the ethylene ionomer resin has a Shore Dhardness of 40 to 80 and a (meth)acrylic acid content of 5 to 25% byweight.
 13. The golf ball of claim 1 wherein the golf ball-formingcomposition is based on a rubber material comprising a polybutadienecontaining at least 40% of cis-1,4 bonds and an unsaturated carboxylicacid or metal ion or both for crosslinking the polybutadiene.